With the rapid progress of the second generation sequencing technology, normal and pathogenic genes of human and animal are analyzed and identified. Unknown problems of biogenetics and auxology are understood on whole genome level. It is indispensable step before gene sequencing to set up library of standard sample suitable to the second generation sequencing plat, which is named library construction in brief. The main methods of library construction now are Trueseq and Nextera systems from Illumia, which are both complicated on operation. During operation of the both, it is necessary to end blunting, adding base A and ligating adapter to one terminus, which are all needed to be operated in purified sample system, as a result every step must has purified operation. While as technological limitation, it is inevitable to have some sample loss for purified operation, which result in large beginning amount of DNA, at least nanogram level, and a huge amount of information loss during library construction. For trace sample, such as scarce sample or sample from clinical patients, traditional library construction methods are not suitable. In conclusion, there should have some improvements on gene library construction methods of the second generation sequencing technology.